1. Field of the Invention
The present invention relates to magnetic recording media used in a high-density magnetic recording and reproducing apparatus, a method of manufacturing the magnetic recording media, and a magnetic recording apparatus.
2. Description of the Related Art
Magnetic recording apparatuses such as hard disk drives (HDD) are widely used accompanying spread of personal computers. In recent years, the advent of the Internet and DVDs for high-definition image information has rapidly increased the amount of information to be handled, leading to a growing demand for an increased capacity of HDDs. More and more small-sized HDDs are mounted in mobile instruments such as cellular phones, car navigation systems, and MD3 players. More and more expectations are thus placed on an increased recording density. Such a situation is resulted from a significant increase in the recording density of HDDs. The recording density of HDDs is increased by forming smaller magnetic recording marks. Formation of smaller marks requires a smaller write head, a read head that can detect a lower magnetic field, and magnetic recording media to which smaller marks can be stably written.
In order to form smaller marks on magnetic recording media, efforts have hitherto been made to reduce the size of magnetic particles forming a magnetic recording layer deposited by sputtering. However, reduction in the size of magnetic particles has been more and more difficult owing to the degraded thermal stability of fine magnetic particles, that is, a so-called thermal fluctuation problem. In order to solve the thermal fluctuation problem, it is conceivable to improve the thermal stability of a magnetic material itself. This solution instead enhances resistance of the magnetic recording layer to a recording field, thus requiring a high magnetic field in write operation. However, the field intensity achieved by a write head is approaching a limit.
Under the circumstances, a patterned media has been proposed, which has a structure greatly different from that of conventional magnetic recording media. In the patterned media, recording cells serving as minimum recording units are arrayed on recording tracks by lithography. In a conventional magnetic recording layer deposited by sputtering, even a minimum recording mark is formed by writing data to a cluster of several tens to several hundred magnetic particles. On the other hand, the patterned media enables the size of magnetic particles to be increased to that of a recording cell formed by lithography. This makes it possible to fundamentally solve the thermal fluctuation problem, attributed to a reduction in the size of magnetic particles.
However, since the pattered media has finely processed recording cells, when the head collides against the media, the recording cells themselves are likely to be destroyed by the resulting impact or friction. A recording cell consisting of a single magnetic particle has its magnetic characteristics markedly changed even with a fine defect. In the recording density estimated to be realized by the patterned media, spacing between the head and the media will be further reduced. Higher demands are thus expected to be placed on the resistance to the collision or friction.
In order to improve the resistance to the impact or friction between the head and the media, a hard diamond-like carbon film is commonly adopted as a protective film on a recording film (see, for example, Jpn. Pat. Appln. KOKAI No. 2004-295989). However, the surface of a diamond-like carbon film deposited by chemical vapor deposition (CVD) does not easily allow the adhesion of a lubricant. Thus, disadvantageously, the lubricant may fail to adhere to some areas of the diamond-like carbon film, or, at the time of the contact, the lubricant may be released and adhere to the head.
On the other hand, various surface treatments have been proposed which serve as methods for improving the adhesion for the lubricant. However, if the entire surface is improved so as to allow the lubricant to adhere easily, large capillaries are formed when the head comes into contact with the media surface. This increases sticking force for the head to do more serious damage to the media as a result of friction. A tradeoff relationship thus exists between improvement in wettability and reduction in the spacing between the head and the media. Particularly with the patterned media, if the lubricant does not adhere well to the media surface and fails to adhere to any areas, each magnetic particle is seriously damaged. It is thus essential to realize uniform adhesion of the lubricant.
In order to solve this problem, a method has hitherto been proposed which forms recesses and protrusions on the surface of the media. Forming recesses and protrusions on the surface of the media separates minutely each area in which the lubricant is present, thus improving the adhesion of the lubricant. A very small space can also be created between the head and media at the time of contact. This prevents the release of the lubricant at the time of the contact as well as an increase in the magnitude of friction caused by stiction of the head. However, with an increase in recording density, the uneven structure prevents reduction in the spacing between the head and the media.
No techniques are currently known which can solve these problems to improve the durability of the patterned media.